Topic 2 Flashcards
What are the characteristics of life?
order regulation energy processing growth + development reproduction response to environment evolutionary adaption
What did Aristotle say?
species are fixed = unchanging
they are created perfectly matched to their environment
organized by complexity, with man on top
What is taxonomy and systematics?
nomenclature: a system of rules for naming things
taxonomy: the practice of naming + classifying organisms
systematics: the theory (and practice) of classifying organisms based on evolutionary history
What are the problems with common names?
different names for some species, common names differ among countries and languages, problem can occur within the same language and country
same name for different species
common name may imply relationships that do not exist
What is the Linnaen System?
use of Latin as universal language of scientific nomenclature
use of unique binomen as name of each species
classify and group species using hierarchical categories based on relatedness and/or similarity
What is a binomial name?
genus name, species name together make the binomial name
What are phylogenetic trees?
evolutionary tree that shows the evolutionary relationship between organisms (past and present)
also hypothesis for the evolutionary relationships
goal: to organize species into groups with common ancestory
What is a taxon?
named group at any level of classification
What is a clade?
a valid group includes the ancestor at any node and everything above and beyond it (descendants)
How do you interpret a phylogenetic tree?
relationships among taxa are interpreted from order in which branches split, not from how names of taxa are arranged at tips of branches
a tree can rotate at its nodes (like a mobile) without altering the relationships
What is the in group and out group in a phylogenetic tree?
in group: group whose relationships interested in untangling
out group: one or more taxa that are distinctly related to the in group, but that have diverged from it at an earlier time
What is character and state?
character: type of structure, behavior, DNA sequence, etc.
state: manifestation of that character
What is the principle of parsimony?
construct a set of nested relationships that minimize the number of times a character changes states
choose the phylogeny that requires the fewest number of evolutionary events —> because it is more probable
What is Occam’s Razor?
if one must postulate a number of unknowable events (changes in character states), the best hypothesis is the one requiring the fewest postulates
What is synapomorphy?
relative to non-vertebrates, presence of vertebrate is a synapomorphy (shared, derived state)
only synapomorphies are useful for reconstructing phylogenetic relationships
What is symplesiomorphy?
within the vertebrates, the trait is a symplesiomorphy (shared, ancestral state)
What is a homologous characteristic?
look the same and have the same evolutionary origin
What is an analogous characteristic?
appear the same but actually evolved independently (convergent evolution)
What is molecular phylogenetics?
matching of bases in selected gene sequences
mutations can cause changes in bases
changes accumulate over evolutionary time
more matches between species –> more likely to be closely related
What is convergent evolution?
independent evolution of similar traits in different lineages
What is a monophyletic group?
contains a common ancestor and all of its descendants and no other unrelated taxa –> clade
an ideal taxon = monophyletic group (clade)
must use traits that are similar because of common ancestry
structures in different species that are acquired from common ancestry are homologous traits
What is a polyphyletic group?
taxa get clumped together even though they do not share recent ancestors
created because we don’t understand things
more than one common ancestor (possessing different ancestors)
lacking common ancestor that unites members in group
incorrectly grouped by superficial similarities, not due to common ancestry
What is an example of a polyphyletic group?
including bats with birds would create a polyphyletic group
incorrectly grouped by a similar characteristic, not due to common ancestry
What is a paraphyletic group?
groups that do not contain all descendants of a common ancestor
often the result of the removal of taxa that are highly divergent from the rest of their clade
usually make mistake because some descendants appear different from other members of clade
